How to Get Rid of Rust in Motorcycle Gas Tanks

Ever look inside the gas tank of an old motorcycle and see nothing but rust? It's really common and there are products out there to either get rid of the rust or supposedly coat and seal the tank. Well, maybe, but, since a chemical reaction caused it, why not reverse the whole process and really get rid of it?

I was flipping through the pages of the latest Motorcyclist Retro and found an article showing the straightforward process of electrolysis using a battery charger, washing soda and a bit of wire. You combine the simple ingredients, fill the tank, insert the wire anode, turn on the current and let the fun begin. A couple of days later, no rust.

If you're the type of guy who likes to restore old bikes, next time you run into a rusty tank, give this a shot and see how it turns out. It works on smaller individual pieces, too. Pretty cool.

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Comments

About 3 or 4 years ago I finally convinced my dad he should get the chopper he built when he was 18 running again. Everyone told us just to sandblast it or toss but my mother’s an artist so she painted a pinup on the tank back in 72 so we wanted to keep the tank as is. We bought this product that was a chemical rust remover and a second chemical that coated inside of the tank in a plastic film of some kind.

JR’s right. Clean metal will most definitely start rusting immediately if it’s not protected somehow. This is only half the process; it needs to be followed up with a coating to prevent the rust from coming back.

You wouldn’t leave a bare steel surface on the outside of your bike without at least putting a clearcoat over it, so why do the same inside your gas tank?

Protecting the clean rust-free metal is fine once it’s rust free. The problem is getting to that point when the tank is already corroded. This method gives you a great starting point to begin your preferred rust preventive strategy.

You often see bikes for sale on eBay with at least one photo looking down into the tank to show the condition of the interior so you know what you’re getting into. If this method can save a rare tank filled with rust, it seems to be worth a shot and it certainly isn’t expensive.

This all depends on the degree of deterioration to the tank in the first place. If there is only a wafer thin layer of metal left your better off sourcing a new tank. Then of course a PET sealer or something similar. Expect your tank to be sitting round for a week or so.
Neat idea, i know it’s used to clean coins and aritfacts but the thought never occurred to me to use it to clean bike parts.
Kudos

Why coat them if they are rust and hole free.
The tank did not have coating on before it got rusty did it? the only tanks that are factory coated that I know of are BMW and Harley tanks.
the trick is to neutralize the the reaction and dry the tank. for example I would wash it with a baking soda water mix to absorb any acids, rinse and clean with a solvent (mineral spirits , alcohol, lacquer thinner) and make sure you store your bike with a full tank.
this process should be the same if you were going to Kreme the tank.
I do however seal the inside of a tank if I weld on it because the welding actually weakens the metal and it sucks if fuel leaks through and ruins your paint.

Re: Tank Lining. As mentioned in the article on 650 Rider, phosphoric acid can work well. It is available at paint stores to seal up any last remaining rust that is hiding in the tank. It converts the Iron Oxide (rust) to Iron Phosphate, which stable and will not grow like rust.

Ultimately, a tank that is full of gasoline will not rust. Of course, one should also burn the gas regularly to avoid varnish deposits. Oh my!…that would imply riding the bike, too. That is not a bad thing either.

As mentioned before above, phosphoric acid is a very effective solution to clean and prevent the rust to re-appear. Clean the tank first with water + sand (don’t forget to flush the sand ;-), clean with phosphoric acid, and use a coating product if you’re a perfectionist … I’ve used this method a few times and it always gave great results.

The electrolysis method needs line of sight to work effectively,a straight path from the electrode to the affected area, and no touching, or you will have a short.
Home Depot sells phosphoric acid in their paint section abouy $13 a gallon. Equally effective is plain white vinegar, it will dissolve the rust if you have time. Nuetralize with baking soda.

I actually have used this method to de-rust a tank, (75 CB750) and it worked ok. We used oxy-clean instead of washing soda (easier to find, essentially the same stuff) and left the anode in the tank for a few days. One BIG problem we had was that the rust would flake off the tank, float around on the surface bubbles, and eventually touch the anode and short circuit the whole thing. Naturally this would happen at night, when we weren’t paying attention. After that we did an acid wash and a NAPA tank sealer. We were pleased with the results, but I wonder if just a thorough acid wash would have done just as good of a job.

Please, if you try electrolysis process remember this gives off hydrogen.
NO sparks anywhere!
Also there is a black oxide residue that needs to be thoroughly cleaned off for any other coating to adhere well.
Maybe that “650 Rider” can advise.

I urge any motorhead that hasnt done this , to go out in the shop right now and cook up a rusty old pair of pliers or something .

Good to see you mentioned it . I have found it an indispensible tactic for freeing the exquisitely stuck machines that find their way to me , so I made up a little site some years ago to help spread the word .http://royalcrossfarm.com/electrolysis.htm
Oil grease and varnished fuel will hamper things , TSP cuts through them somewhat, but not when its a 1/2 inch thick .

Check out the results achieved with ordinary feed mollasses while you’re there .

I’ve read about this just never thought about trying it on a gas tank . I think I’ll give it a try . Does anyone have the proper ratio of water to mollasses mix to achieve the results of the above post ?

I’ve used this method to clean up old Stanley Bailey wood working planes, and it is very effective. You do need *line of sight* between the tank and the anode for it to be effective. Cranking up the voltage speeds the process.

In short this is an effective method of eventually reversing the rusting (oxidation) process. And, keeping the tank full with gasoline will keep it from rusting again once it is clean.

I,ve been using molasses mixed roughly 1 part to 4 parts water for years to get rid of rust only, on parts before I zinc plate them. but you must clean the parts totally of any paint , grease, heavy rust etc, The worst gas tanks I’ve seen for rust are late model Ducati Tanks, within 12 months they are leaking. Fortunately they have big gas cap opening and you can get your hand inside, I Kreem’d them all.

I used this on my 77 GL1000 tank, because removing it to shake it around was not really an option (under seat tank that requires taking apart the bike.) It worked very well. I used A&H washing soda and a piece of angle iron and cleaned it every few hours. The larger the anode the faster the derusting. Remember, more power means more hydorgen bubbles! Also, replenish the evaporated solution frequently to make sure you clean the top of hte tank too. It does not need direct line of sight, but it helps.

I’ve cleaned/sealed over 60 motorcycle tanks.
Not all are rusty, some are loaded with dried
gas/oil residue. And some have had the misfortune
to have been coated with the junk known a Kreem.
I use muriatic acid to remove rust.It does not eat
good metal if there is rust to eat, and it only takes a few minutes to remove heavy deposits. Just get it out as soon as the rust is dissolved. The other cleaners and sealer I use are from the POR-15
company.

i have a new steel oil tank for my chopper and it has surface rust inside it,i need to find a way to clean this out,is there a chemical out there that can do this without having to seal the tank afterwords to keep the rust from returning?

Hi i have just bought a 1995 suzuki dr 650 which has been stood in a garage for the last 18 months…it has a rusty residue when i de-attach the fuel pipe from the carb, it will run alright for a few mins then die and sometimes wont rev much like its got a fuel starvation problem… I really need to know the cheapest possible solution to sort this as im skint…Any replys would be greatley appreciated,,,,Thanks,….Martin

Martin R, your fuel is bad, the tank is probably fine. Drain it out and put some fresh fuel in. Your carb may be gummed up a little inside (probably not too bad). Go down to a Yamaha dealer and ask for some “carb cleaner”. Not the spray kind but the kind you pour into your float bowl and run through the running engine.

Your petcock (fuel tap) has a vacuum line running to it. Be sure that this is connected to the intake manifold or use a vacuum gun on the end of it. This allows the fuel to flow when the engine is running. If this isn’t connected or working poorly you will have problems with fuel flow. You should be able to turn the tap lever over to “PRI” and allow fuel to run to the carb freely.

I have motorcycle with a rusty tank and have read through all of these posts. They have given me some options that i would find most economical and very creative. Thanks for all the help everyone.
Todd